More specific stats on that, Two handed swords will gain 20% damage and 5% crit when used with smash, usually not enough to push it to being above dual swords in offense, but keep in mind you're also only repairing one weapon! It's an expensive one but I'd be willing to bet it's cheaper to repair 1 2hander over 2 swords, presuming the swords aren't cheapos. I don't think windmill gains range with a 2hander, but I may be wrong. 2handers are in essence the late game economy option.
Single handed sword and shield is oddly enough great for people that play offensively or otherwise get themselves into trouble more often then they probably should, as defense can be loaded while the ending animation of a lot of attack skills is playing, allowing some defense on a whiffed/ineffectual attack. I like it! But it can be as expensive if not moreso then dual wielding, as shields are expensive, and blocking with them lowers durability. A perfectly effective option, but keep that in mind! If you're interested in practicing with it, round shields are pretty good, while still being fairly cheap. Another bonus is being able to block arrows/magic with defense which you will quickly find out is a big deal.
Dual Wielding is the best offense you can get with generic melee (aka close combat). Two swords means double damage on all normal attacks, I dunno if skill damage is doubled, but I think it at least adds to it a bit. Probably the most expensive/second most at least. Notable advantage, humans can only use final hit with dual swords, a very powerful skill that lets you teleport around and permastun an enemy. It's VERY good. If you are not human you can't get this, nor can you dual wield at all (unless you're a giant in whichcase you can dual wield blunt weapons. You however, cannot get final hit. Giants also get super good shields for comparatively low prices, along with the fact that a lot of their one handed weapons have 2 hander damage.)
SO YEAH. Welcome aboard. I'm hopping on now and will get you in if ibid hasn't beat me to it.